1871.] JTJDD PUNFIELD FORMATION. 217 



a. Beds of light-coloured sometimes pinkish sand, in places 

 interlaminated with bands of clay. They contain much 

 carbonaceous matter, seams of lignite and nodules of 

 pyrites about 30 ft. 



h. Beds of grey and whitish laminated clay (with much 

 lignite in places) and bands of nodular ironstone. These 

 ironstones contain casts of shells, very imperfectly pre- 

 served, including Ostrea, Cardium, Gorbula, and Ceri- 

 thium. I regard these as the equivalent of the " oyster- 

 beds of Punfield." 30 to 40 ft. 



c. Thin well-marked band of ironstone, very hard and dark- 

 coloured, only a few inches thick. This bed is in 

 places crowded with vegetable markings, and contains 

 casts of marine shells. This bed rests directly upon the 

 variegated beds of the Wealden, and seems to represent 

 the " marine band of Punfield." 



3. Mewps Bay. At this place, which is 1| mile "W. of Wor- 

 borrow Bay, the very dimiBished representative of the Upper 

 Neocomian (" Lower Greensand ") is faulted against the variegated 

 beds of the Wealden. The same is the case in Bacon Hole a little 

 farther west. 



4. Lulworth Cove. This section is about one mile west of the 

 former. On the eastern side we find lying directly upon the varie- 

 gated beds grey clays with ferruginous bands containing much 

 wood and vegetable matter, and also a few casts of shells, none of 

 which are determinable. There appears to be here no trace of the 

 Upper Neocomian (Lower Greensand), which is probably either 

 quite overlapped by the overlying Cretaceous beds, or has altogether 

 thinned out. 



lY. Sections in the Isie oe Wight. 



The nearest Isle-of- Wight section of the Wealden strata, that of 

 Compton Bay, is situated thirty miles due east of Punfield Cove. 

 As, however, the clearest exhibition of the representatives of the 

 Punfield formation is that in Brixton Bay, a little to the west of 

 Atherfield Point, I propose in the first place to describe this in 

 some detail, and then to point out in what respects the sections of 

 Compton Bay and Sandown Bay difier from it. 



Considerable diversity of opinion has existed among geologists with 

 regard to the correlation of the Wealden beds of the Isle-of- Wight 

 with those of the Weald-area of Kent, Surrey and Sussex. 

 While Dr. Fitton * regards the upper grey shales and limestones as 

 representative of the Weald Clay, and the sands and variegated 

 beds below, as equivalent to the Hastings Sand, Mr. Bristow t 

 considers the whole of the Isle-of- Wight series referable to the 

 former subdivision, and believes that the latter is not represeiited in 

 the island. The manner in which the Wealden beds thin out 

 rapidly, or change their mineral character laterally within short 

 distances, will always render any attempt at correlating their sub- 



* Trans. Geol. Soc. Ser. 2, vol. iv. p. 184, et seq. 



t Memoirs of the Geological Survey, Geology of the Isle of Wight (1862), p. 8. 



